This invention relates to a process for producing a heat-resistant and moisture-resistant polyborometallosiloxane.
Polyimide is known to be a polymer having excellent heat resistance which does not easily melt or decompose at high temperatures. It can be prepared, for example, by poly-addition reaction of pyromellitic dianhydride and 4,4'-diaminodiphenyl ether to form a polyamide acid prepolymer, and heating the prepolymer to 250.degree. C. to dehydrocyclize it. A polyimide film is used mainly as a heat-resistant insulating material because it does not decompose even when heated in the air to a temperature near 225.degree. C. The advent of heat-resistant polymers which are stable at higher temperatures is strongly desired in the field of high temperature technology. The present invention can provide a polymer which meets this requirement.